1. Technical Field
This invention relates to a weaving machine, and more particularly to a bias-weaving machine suitable for forming three-dimensional woven structures.
2. Background Information
The use of textile preforms is well known in the composite industry. Such preforms are commonly fabricated using relatively simple weaving machines that typically produce flat, substantially two-dimensional woven products with yarns extending in only two directions. Such materials are generally formed by interlacing two sets of yarns substantially perpendicularly to each other. In such two-dimensional weaving applications, the 0 degree yarns are referred to as warp yarns, while the 90 degree yarns are referred to as fill yarns. The introduction of bias yarns (e.g., interwoven at 45 degrees, into the weave is also known to produce materials having superior shear strength and off-axis tensile strength.
Three-dimensional preforms are often formed by joining a plurality of two-dimensional woven materials, for example into “T” or “Pi” shapes. Typically, simple two-dimensional woven fabrics are produced by a material supplier and sent to a customer who cuts out patterns and lays up the final preform ply by ply. Such joining operations are typically time and labor intensive and therefore expensive. Moreover, composites formed by such operations are known to sometimes have compromised mechanical properties at the joints and between the various plies. In other applications, a bias cloth may be laid up with three-dimensional woven preforms having only fill and warp yarns. While such a process may reduce time and labor requirements as compared to a full lay-up, it remains expensive. Moreover, delamination between the bias cloth and the woven preforms is a common problem.
One approach to overcome such difficulties in forming three-dimensional woven preforms is to weave the bias yarns among the warp and fill yarns. One attempt to provide such functionality is described in U.S. Patent Application Publication No. U.S. 2002/0069927, entitled Three-Dimensional Woven Forms with Integral Bias Fibers and Bias Weaving Loom, published on Jun. 13, 2002 (hereinafter, the '927 application). This approach, however, is not without its drawbacks. Therefore, there exists a need for an improved weaving apparatus for forming three-dimensional woven structures including a plurality of bias yarns, such as those required for advanced composite material applications.